Prius Tire Tuning

Well, at least you're being honest with the people.

For once.

So you DON'T care about braking performance of the tires. You DO care about...what? Trying to make yourself look like some know-it-all about the Prius with all your pretty charts and graphs? Charts and graphs that you have admitted have nothing to do with facts and everything to do with your fantasy world?

Facts. When asked for them, you choose not to give them--because that might upset your fantasy world.

You know, you can't pick and choose the facts. They are what they are. Facts aren't obligated to preserve your fantasy world.

Come on, do tell us MORE about how you don't care about the facts.

The tires do something, the car does something, the physics do WHAT?

You've made the claim; now it's up to YOU to put up some facts and data. No, it's not "everything is as *I* say it is unless someone else can prove me wrong, la de da" as you say. You claim it, now YOU back it up.

Or are you saying that your claiming it makes it de facto the truth? Is that what you're saying, Bob?

You have no idea whether or not it "stops like it did before" because you haven't measured braking distance, either before OR after tire changes. You just like to make claims out of thin air, and you HATE it when someone calls you on it and asks you to back up your claims.

What, your pretty charts and graphs not doing you any good right now? You claim to have all SORTS of data on fuel economy--but that same "scientific method" you use is suddenly useless or invalid when it comes to actual data on braking performance across tires?

So you just declare what you say to be factual, eh?

Go ahead, bring something to the party. You won't--and that will tell all about YOU.

Again.

La-dee dah, 'Elmo'. You're such a cheap and easy puppet.

Bob Wilson

. . .

I've had a chance to read the article throughly and it is about the practice of increasing the size of the wheel and installing low profile tires. So right off the bat, the density of the wheel/tire changes as there is more metal and less air. In contrast, I'm using the exact same alloy wheels the car came with, no additional metal.

So let's go over the quoted elements and their impact:

"Obviously, a wheel with the same mass at a larger OD has a larger rotational inertia than the OE wheel." Absolutely and this is an improvement in Prius handling. The steering even with perfect, four- wheel alignment is a best neutral stability. However, the higher rotation inertia of the larger tire improve steering stability. I observed this on a trip to Madison Wisconsin from Huntsville.

I drove up with the Toyota replacement, the 175/65R14, on the front and the experimental 175/70R14 on the rear. That Sunday I swapped front and rear and highway steering stability was improved to the point of making the drive home easier. In contrast on the drive up, I had to keep constantly on high alert to keep the car between the lines. On the way back, the car tracked true.

As for the other effects, they used a lot of "may" and ". . . there is a significant lack of public domain data available to assess these effects." After all, they aren't 'Elmo' who acts as if asking a question can substitute for research and experimentation. These are serious folks to don't ask silly questions as much as proposing where they and serious people will go to investigate.

Now this paper does discuss one risk and the experimental vehicle is a tall, SUV body which are notorious for that risk. In contrast, the Prius takes corners like they are glued to the road ... they have a lot of margin. I know the larger tires have not impacted my ability to take a sharp turn.

The one effect, a larger moment of inertia, has been found and it is exactly what the Prius highway steering needs. As for the one risk in the paper, the Prius was already superior and my driving has yet to find a problem. The Prius is so good at taking a turn that it can be uncomfortable and scary to those who are not prepared.

I'm still reading the papers and having a great time. I feel like I've walked into a University library and that has been one of my first loves.

Bob Wilson

SURE, bob. SURE.

Glad to contribute. I have seen prior mention of steering/hunting and tracking/wandering issues, the attempted cure for which are aftermarket strut and chassis stiffening braces. Increasing rotational inertia via tire sizing and profile could be a more direct as well as less radical solution.

. . .

I've seen some references to changing the caster but these were not single part changes. To do it right, I would need a sophisticated suspension alignment tool along with a lift. I could do it but the cost, labor and tools makes soon evaporates the fun.In contrast, changing tires is relatively easy and there are a lot of articles in the racing community about tire effects and tuning during a race.

I'm waiting for a strut to fail before tackling suspension changes. I have looked for variable stiffness shocks but they are unGodly expensive parts. It looks like installing shims could shift the caster offset, a bit. However, the articles I've read indicate we would also need to change some of the linkages.

I've read a number of reports about how adding a stiffening plate improved NHW20 handling. But we have the earlier NHW11, a sedan-style, shorter, stiffer body, and the ZVW30 which has been built stiffer. I've not seen reports that 'neutral steering' was a problem with the NHW20 and the ZVW30 handles more like our NHW11 with larger diameter tires ... which they are. The NHW11 uses stock 14" rims and the ZVW30

15" rims.

BTW, I was looking for something else in my archives and found this photo showing the tires I've tested:

Bob Wilson

Den 19.05.2011 16:35, skrev Elmo P. Shagnasty:

LOL, why would he give you data of any kind. You don't believe him anyway.

hPSa

Oh, I get it. Mr. Charts and Graphs doesn't have to provide actual data, yet the world is supposed to believe him.

On May 20, 2:16 pm, "Elmo P. Shagnasty" wrote: . . .

This goes to the heart of the matter. I use data, often plotted, to make sure I understand how the real world works. I don't mind sharing this with others but first the real world has to persuade me. In contrast, you bring no facts and data.. Instead, you substitute rhetoric and worse.

The natural world is a hard task master and doesn't befriend fools . . . and neither do I. But I'm not above exploiting the a fool's folly:

Given both tires have the same pressure, one of the reasons for using Sumitomo T4s, easily achieved. So the larger diameter tire has less flex than the smaller diameter. This avoids the flex heating: This flexing heats the tires by tread, which leads to improved alignment and lower rolling drag. So I'm reminded of Bob Dylan's words:

". . . wish that for just one time You could stand inside my shoes And just for that one moment I could be you

Yes, I wish that for just one time You could stand inside my shoes You'd know what a drag it is To see you"

Bob Wilson

Except for when you don't--like with braking performance. You provide no data about braking performance on different tires, yet you happily claim that there is no difference--simply because "you say so".

That puts all of your "data" to question.

In contrast, nature is consistent and doesn't really care about whining children with a keyboard which is what I like about this chart showing tire heating effects:

The right hand temperature bands are from a tire with excess camber and was confirmed with edge wear. To correct it, I bought a camber adjustment bolt and the tires wear evenly. But the real takeaway is the tire, relative temperature, the Y-axis. Rolling friction generates heat and warming the tire is a direct effect. Notice too that higher pressure leads to less heat.

Bob Wilson

...which has nothing at ALL to do with braking performance, which you declare to be "the same" despite your total lack of data--

--and then you demand that if the world doesn't like your declaration, it's up to the world to prove you wrong.

Yeah, bob. Sure.

On May 21, 7:10 am, "Elmo P. Shagnasty" wrote:

.. . . (troll scat that will soon disappear)

As I was saying:

Prius alignment is normally limited to just front toe, the angle the tires are pointed inward or outward. Camber is the vertical tire angle and on the front and may require a new camber bolt, ~$7.00. Toyota documents a rear wheel toe adjustment but it requires a special tool that appears to bend part of the rear axle, a smaller version of a frame bending.

Another approach is to use shims that adjust the rear wheel hub, mounting bolts. Each hub is held by four mounting bolts:

upper tube is the brake line, the round sensor is the rotationsensor used by the ABS. The four bolts hold the hub to the axle. Butthere are two shim styles available, tab and disk. The tab systems come with a box of assorted sizes, ~$15-25. Pairs of shims are put on adjacent bolts, vertical pair for toe and horizontal pairs for camber: putting them on in pairs, there won't be any rocking motion afterthe bolts are torqued. If anyone wants to try the metal tabs, I haveleft-over tabs and have no problem with sending a set for both rearwheels. Send me an e-mail with your address and Prius make and model. First adjust the wheel with the worst toe. Then put tabs in the opposite wheel to adjust camber. Sad to say, a certain amount of experimentation is needed: first put a pair of 1/32 inch shims on on rear wheel and instead ofdecreasing the toe, the pink and red lines, it made it worse. So Iremoved those and put a 1/64 inch shim on the front and the toe forboth rear wheels came right into the value I was after, nearly zero. Wheel alignment measurements can be expensive so I bought a life-time alignment service from Firestone. I understand other tire chains offer similar services but check the terms and conditions. So far, Firestone has been very good about it and I only go back for a second reading if I make a change. Sad to say, none of them have figured out that perfect, four-wheel alignment could be a nice profit center.

In a similar fashion, I used a pair of 1/16 inch shims on the opposite hub and over corrected. Replacing them with 1/32 shims brought both rear cambers to nearly zero. Notice that changing the camber had a very small impact on toe.

The other shim style are two, slightly tapered disks, the EZ shim system, ~$15/disk, two required:

Using a table or the Specialty Products online tool, the numbers around the edge are rotated so the two disks correct both toe and camber. Tabs are removed for the bolts. This is the system I'm using now.

I switched because the metal tab system will always leave a gap between the hubs and axle:

ends to the metal tabs can be seen sticking out of the hub-axlemating in the bottom-center of the photo. But you can see theaccumulated road grime on the black painted axle and this is notsomething one wants between the gap. We seldom have salted roads in North Alabama but any gap is a place where air and water, especially salt water, can come in and rust or corrode the gap. Although the zinc coated tabs are probably OK, they remain another potential source of corrosion. In contrast, the plastic disks blocks water and air and can't corrode. They are available from Amazon: Excessive camber leads to one side of the tires wearing out first. But poor alignment, especially toe, can make Prius steering and tracking unstable as well as wearing out the tires. So before trying different diameter tires, make sure the alignment is as perfect as possible. Then increasing the tire diameter, especially for the front wheels, completes the job. It also improves braking stability by preventing wheel asymmetry from coupling with the braking forces.

Bob Wilson

Show us again, bob, where is your data regarding actual braking distances--and not just your claims that "well, the car braked"?

We're still waiting for your actual data that PROVES what you claim.

What, no charts and graphs?

Another boring driving day as the car ran and the brakes worked just fine. With the warmer temperatures, it showed 62 MPG for the 26 miles I drove on Friday. It really is a superior car.

Bob Wilson

The question was, Bob, do you have actual data to back up your claim that braking distance/performance is unaffected by changing tire sizes?

You don't. All you can say is that they "worked just fine". No data whatsoever.

Is that what your pretty charts and graphs are full of? Random "I say so therefore it is" numbers?

Certainly if some numbers show up that you don't like, you simply ignore them. That seems to be how you do things.

Well La Dee Dah, 'Elmo.' The funny thing is I have the tools and skills to measure braking distance.

About a year and a half ago, we started hearing reports at PriusChat of an intermittent braking problem with the ZVW30 Prius. We conducted a survey and found ~50% had not experience it (including me); ~30% had but didn't consider it serious and; ~20% considered it serious.

So in parallel, I started collecting reports and document the conditions:

. . With this we were able to identify patterns: a significant bump, slow speed, modest braking, and slippery conditions. Still, I could no reproduce it so I decided to buy some accelerometers to see what is going on.

So sitting on the table within arms reach is one of my two recording accelerormeter:

by Gulf Coast Data Concepts, it is a terrific tool and I boughttwo of them. One has a LiON battery and the other uses a AA batterythat I loaned to others reporting the braking problem. With this tooland the collected reports, I was eventually able to replicate thebrake pause and quantify the effect: About the same time, Toyota announced a brake recall, SSC-A0B, that changed the software in the brake controller. So I went back and verified the pause was gone at two different locations: Measuring brake problems takes instrumentation and skills and Toyota's fix worked perfectly. As for my tires, the ABS works just fine. Still, an idiot's "question" can be useful in this case by introducing and reviewing how braking performance is measured.

Bob Wilson

ps No, 'Elmo' is not my sock puppet ... just another especially unskilled tool. You are so much my bitch.

The question was, where are your data concerning braking distance?

The data beyond "it brakes just fine"?

The funny thing is, you have refused to acknowledge that "it brakes just fine" isn't actual data, instead insisting that "it brakes just fine" is actual data.

Apparently, that's what you mean by "you have the tools and skills to measure braking distance".

"It brakes just fine." Mr. Factual strikes again.

. . .

Good morning,

Let's see, an Answer for you?

Now I'm ready to give it to you though I don't think that you're going to like it. You're really not going to like it. The Answer to the Great Question is:

Bob Wilson

ps. You are so my bitch.